Citations

Atherosclerosis is the major cause of adult mortality in the developed world, and a significant contributor to atherosclerotic plaque progression involves smooth muscle cell recruitment to the intima of the vessel wall. Controversy currently exists on the exact origin of these recruited cells. Here we use sex-mismatched bone marrow transplant subjects to show that smooth muscle cells throughout the atherosclerotic vessel wall can derive from donor bone marrow. We demonstrate extensive recruitment of these cells in diseased compared with undiseased segments and exclude cell–cell fusion events as a cause for this enrichment. These data have broad implications for our understanding of the cellular components of human atherosclerotic plaque and provide a potentially novel target for future diagnostic and therapeutic strategies.

Background— Validation of in-hospital mortality models after percutaneous coronary interventions using multicenter data remains limited. Methods and Results— This study evaluated whether multivariable mortality models developed during the pre-stent era by New York State, American College of Cardiology (ACC)–National Cardiovascular Data Registry, Northern New England Cooperative Group, Cleveland Clinic Foundation, and the University of Michigan are relevant in patients undergoing percutaneous coronary intervention in the 1997 to 1999 National Heart, Lung, and Blood Institute Dynamic Registry. Of 4448 Dynamic Registry patients, 73% received ≥1 stent and 28% received a IIB/IIIA receptor inhibitor. In-hospital mortality occurred in 64 patients (1.4%). The New York state model predicted mortality in 69 patients (1.5%; 95% confidence bounds [CI], 0.89% to 1.70%); Northern New England predicted mortality in 60 patients (1.3%; 95% CI, 1.0% to 1.7%); and Cleveland Clinic predicted mortality in 76 patients (1.7%; 95% CI, 1.3% to 2.1%). Among high-risk subgroups, with these 3 models, observed and predicted in-hospital mortality rates in general were not different. The other 2 models yielded different results. The University of Michigan predicted fewer deaths (n=47; 1.1%; 95% CI, 0.7% to 1.3%), and the ACC Registry model predicted 603 deaths (13.5%; 95% CI, 12.6% to 14.4%). Using the ACC Registry model, predicted mortality was higher than observed in each subgroup. Conclusions— Application of 5 mortality risk models developed from different data sets to patients undergoing percutaneous coronary intervention in the Dynamic Registry predicted, in 3 models, mortality rates that were not significantly different than those observed. In both high and low risk subgroups, the University of Michigan slightly underpredicted mortality, and the ACC Registry predicted significantly higher mortality than that observed.

ABSTRACT γ‐Secretase cleavage is the final proteolytic step that releases the amyloid β‐peptide (Aβ) from the amyloid β‐protein precursor (APP). Significant evidence indicates that the presenilins (PS) are catalytic components of a high molecular weight γ‐secretase complex. The glycoprotein nicastrin was recently identified as a functional unit of this complex based on 1) binding to PS and 2) the ability to modulate Aβ production following mutation of a conserved DYIGS region. In contrast to the initial report, we find that overexpression of wild‐type (WT) nicastrin increases Aβ production, whereas DYIGS mutations (MT) have little or no effect. The increase in Aβ production is associated with an increase in γ‐secretase activity but not with a detectable increase in PS1 levels. Subcellular fractionation studies show that WT but not MT nicastrin matures into buoyant membrane fractions enriched in γ‐secretase activity. These data support the hypothesis that nicastrin is an essential component of the γ‐secretase complex. The finding that WT nicastrin overexpression can increase γ‐secretase activity without altering levels of the presumed catalytic component (PS) of the enzyme may point to a role for nicastrin in facilitating cleavage by regulating substrate interactions with the γ‐secretase complex.

Multivesicular bodies are late endosomal compartments containing lumenal vesicles that are formed by inward budding of the limiting endosomal membrane. In the yeast Saccharomyces cerevisiae, integral membrane proteins are sorted into the lumenal vesicles of multivesicular bodies, and this process requires the class E subset of VPS genes. We show that one of the class E VPS genes, BRO1/VPS31, encodes a cytoplasmic protein that associates with endosomal compartments. The dissociation of Bro1 from endosomes requires another class E Vps protein, Vps4, which is an ATPase that also regulates the endosomal dissociation of ESCRT-III, a complex of four class E Vps proteins (Vps2, Vps20, Vps24 and Snf7/Vps32) that oligomerize at the endosomal membrane. We also show that the endosomal association of Bro1 is specifically dependent on one of the ESCRT-III components, Snf7. Our data suggest that the function of Bro1 in the MVB pathway takes place on endosomal membranes and occurs in concert with or downstream of the function of the ESCRT-III complex.

Abstract We tested the hypothesis that cells of ventilator-injured lungs are subject to reversible plasma membrane stress failure. Rat lungs were perfused with the membrane impermeable fluorescent marker propidium iodide and randomized to one of four ventilation strategies. Subpleural lung regions were imaged with confocal microscopy, and cell injury was quantified as the number of propidium iodide–positive cells per alveolus. The number of injured cells was significantly greater in lungs ventilated with large tidal volumes and zero end-expiratory pressure than in lungs ventilated with small tidal volumes and positive end-expiratory pressure (p < 0.01). Cell injury correlated with lung weight gain, change in dynamic compliance, and histologic injury scores. In a second set of experiments, lungs were mechanically ventilated for 30 minutes at high tidal volume settings, whereas propidium iodide was perfused either during or after injurious ventilation. Labeling after removal of injurious stress revealed significantly fewer injured cells (0.25 ± 0.09 to 0.08 ± 0.08, p < 0.01). We conclude that cells of ventilator-injured lungs are subject to reversible plasma membrane stress failure.

ABSTRACT An evaluation of the MicroSeq 500 microbial identification system by nucleic acid sequencing and the Mayo Clinic experience with its integration into a routine clinical laboratory setting are described. Evaluation of the MicroSeq 500 microbial identification system was accomplished with 59 American Type Culture Collection (ATCC) strains and 328 clinical isolates of mycobacteria identified by conventional and 16S ribosomal DNA sequencing by using the MicroSeq 500 microbial identification system. Nucleic acid sequencing identified 58 of 59 (98.3%) ATCC strains to the species level or to the correct group or complex level. The identification results for 219 of 243 clinical isolates (90.1%) with a distance score of <1% were concordant with the identifications made by phenotypic methods. The remaining 85 isolates had distance scores of >1%; 35 (41.1%) were identified to the appropriate species level or group or complex level; 13 (15.3%) were identified to the species level. All 85 isolates were determined to be mycobacterial species, either novel species or species that exhibited significant genotypic divergence from an organism in the database with the closest match. Integration of nucleic acid sequencing into the routine mycobacteriology laboratory and use of the MicroSeq 500 microbial identification system and Mayo Clinic databases containing additional genotypes of common species and added species significantly reduced the number of organisms that could not be identified by phenotypic methods. The turnaround time was shortened to 24 h, and results were reported much earlier. A limited number of species could not be differentiated from one another by 16S ribosomal DNA sequencing; however, the method provides for the identification of unusual species and more accurate identifications and offers the promise of being the most accurate method available.